Fox made an 18-foot birdie putt on the 37th hole Sunday, completing a remarkable underdog run to win the U.S. Amateur at Cherry Hills.

The 21-year-old Fox, from Hendersonville, Tenn., was 2-down with two holes to play against Weaver, from Fresno, Calif., before rallying to force the extra hole.

"This is unreal. This whole week is like a dream to me," Fox said.

Both players earned spots in the U.S. Open next year, and will likely receive invitations to the Masters -- both if still amateurs.

Weaver, a 21-year-old redshirt junior at the University of California, had stayed in front most of the day and when he rattled in a 12-foot birdie putt on the 34th hole, he went 2-up, forcing Fox to win each of the remaining holes to stay alive.

"Once he made that, you know, I thought it was over," Fox said. "I thought it was his day. But I just kind of played my hardest to see where it went ... and then it kind of switched."

A senior at Tennessee-Chattanooga, Fox made an 11-foot birdie putt to win the 35th hole.

Still with a 1-up advantage, Weaver needed only to make a 5-foot par putt on the 36th hole at the 18th green to secure the win, but it lipped out, extending the match to a 37th hole.

"I thought I made my putt," said Weaver, who had been in the lead since the fifth hole before being headed at the end. "I kind of looked away, and I thought it went in, but it didn't. That's golf, but just to see it slip through my fingers, it (stinks). And I know I had a great week and all that, but I'm not thinking about that right now."

The miss on the short putt stunned Fox as well.

"It was like dead center from my angle, and when I saw it bounce out, I kind of gasped a little bit," Fox said. "I think I put my hand over my mouth. I was shocked. And quickly I had to gather myself and go to the playoff."

A shaken Weaver landed his tee shot in the rough, putting himself in a tough spot and needing two more shots to put the ball on the green. Fox then stroked a slow roller on his third shot, with the putt breaking at the end from left to right, before dropping in and setting off a celebration on the green.

His father, Alan Fox, who caddied the first 18 holes before giving up the bag midway through because his blistered-covered feet prevented him from going farther, walked gingerly up to his son to give him a hug. Ben Rickett, an assistant coach at Tennessee-Chattanooga, caddied the last 17 holes.

"I've had blisters for probably three days and I knew it was going to be tough to do 36 today," Alan Fox said. "After the first 18, I talked it over with Steven, the coaches and it was obvious, even in the back 18 in the afternoon that I would have had to give up the bag because my feet were really hurting. So, it was smart decision and Steve picked his assistant coach, Ben, to do this. It obviously worked out, and Ben knows a lot more about golf than I do."

The final had brought together two long shots.

Fox, like Weaver, survived a 17-for-14 playoff to qualify for the 64-player match play field and Fox entered match play as the No. 63 seed, the second-to-the-last player to make it when the original field was whittled from its original size of 312 players from 43 states and 20 countries.

"We knew if he got into match play that it would be good because he's like this. Nothing bothers him," said Mark Guhne, Fox's coach at Tennessee-Chattanooga. "He's one of those guys who can play a bad hole and then he can play a great hole. He's got so much creativity that when he gets in trouble he can escape."

Along his way to the final, Fox beat Chris Williams, the top-ranked amateur in the world and advanced to the championship round by defeating Weaver's teammate at Cal, the highly regarded Brandon Hagy.

"You know, my goal was just to make it to match play the first time, being in my first U.S. Amateur," Fox said. "And I just kept going and kept fighting. I'll never be one to give up. Things can click at any moment. You can find your swing or find your stroke throughout a round, and I just wanted to keep going."